Consolidated Statement of Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Revenues
Premiums									$ 22,357		$ 22,090		$ 21,432
Net investment income									2,889		2,879		3,059
Fee income									323		296		287
Net realized investment gains									51	[1]	55	[1]	264	[1]
Other revenues									120		126		70
Total revenues	6,477	6,512	6,359	6,392	6,373	6,407	6,388	6,278	25,740		25,446		25,112
Claims and expenses
Claims and claim adjustment expenses									14,676		16,276		13,210
Amortization of deferred acquisition costs									3,910		3,876		3,802
General and administrative expenses									3,610		3,556		3,406
Interest expense									378		386		388
Total claims and expenses	6,166	5,342	5,751	5,315	5,595	6,075	7,115	5,309	22,574		24,094		20,806
Income before income taxes	311	1,170	608	1,077	778	332	(727)	969	3,166		1,352		4,306
Income tax expense (benefit)	7	306	109	271	160	(1)	(363)	130	693		(74)		1,090
Net income	$ 304	$ 864	$ 499	$ 806	$ 618	$ 333	$ (364)	$ 839	$ 2,473		$ 1,426		$ 3,216
Net income per share
Net income per share, basic	$ 0.79	$ 2.23	$ 1.27	$ 2.04	$ 1.52	$ 0.80	$ (0.88)	$ 1.94	$ 6.35		$ 3.40		$ 6.69
Net income per share, diluted	$ 0.78	$ 2.21	$ 1.26	$ 2.02	$ 1.51	$ 0.79	$ (0.88)	$ 1.92	$ 6.30		$ 3.36		$ 6.62
Weighted average number of common shares outstanding
Weighted average number of common shares outstanding, basic									386.2		415.8		476.5
Weighted average number of common shares outstanding, diluted									389.8		420.5		482.5

[1] Total other-than-temporary impairment (OTTI) gains were $27 million, $30 million and $7 million for the years ended December 31, 2012, 2011 and 2010, respectively. Of total OTTI, credit losses of $(15) million, $(25) million and $(26) million for the years ended December 31, 2012, 2011 and 2010, respectively, were recognized in net realized investment gains. In addition, unrealized gains from other changes in total OTTI of $42 million, $55 million and $33 million for the years ended December 31, 2012, 2011 and 2010, respectively, were recognized in other comprehensive income as part of changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income.